This invention relates to a carboxyl group-containing siloxane compound.
In general, carboxyl group-containing siloxane compounds are useful for a number of use applications where e.g. organosiloxane compounds soluble in water or alcohols are desired. The above carboxyl group-containing siloxane compounds are useful e.g. as an emulsifying agent for forming usual aqueous emulsions of organosiloxane polymers or in their applications upon e.g. alcohol-based cosmetics. Further, as to the compounds it is possible to expect their strong adhesion onto inorganic materials and modify the surface of the materials to impart to the surface, functions such as water repellency, stain resistance, non-adhesive properties, heat resistance, abrasion resistance, etc. For example, as disclosed in Japanese patent application laid-open Nos. Sho 53-10882/1978 or Sho 57-10145/1982, the compounds have been used as an ink-repelling material for litho printing. As described above, carboxyl group-containing siloxane compounds are useful as an emulsifying agent or a surface modifier for inorganic materials.
The state where carboxyl group is bonded in conventional carboxyl group-containing siloxane compounds is expressed by the general formula ##STR2## wherein s is an integer of 2 to 4, as described in Japanese patent publication Nos. Sho 40-20279/1965, Sho 41-236/1966, Sho 42-6519/1967, Sho 49-4840/1974, etc. The present inventors, however, have found that such conventional carboxyl group-containing siloxane compounds are stable to heat in the case where they have a number average molecular weight (Mn) greater than 1,000, but they are decomposed by heat in the case of Mn of 1,000 or less, and have made intensive research on a manner of having carboxyl group bonded to Si atom. As a result we have found that when a polyoxyethylene chain is bonded by the medium of a bifunctional molecule, the above compounds are stable to heat even in the case of low molecular weight.
As seen from the foregoing, the object of the present invention is to provide a carboxyl group-containing siloxane compound, whether its molecular weight is low or high, having a superior heat stability, and useful as emulsifying agent, surface modifier for inorganic materials, etc.